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SPIRILLA RESEMBLING CHOLERA. 339
produces indol, and is highly pathogenic for rabbits,
guinea-pigs, pigeons, and mice.
Spirillum Bonhoffi.—This organism (Fig. 94) was
found in water by Bonhoff. It has a decided resem-
FIG. 94.—Spirillum Bonhoffi, from a culture upon agar-agar; x 1000 (Itzerott
blance to the cholera spirillum, but is rather stouter
and less curved. Curved forms—i. e. semicircles, sig-
moids, and spirals—occur in old cultures especially.
These organisms are colored badly with ordinary stains,
dahlia seeming to be the most appropriate color, and ac-
complishing the process better if warmed. The organ-
ism is motile, and has a long flagellum attached to one
The colonies develop slowly upon gelatin plates, first
appearing in forty-eight hours as little grayish points.
The margin of the colony is sharply circumscribed ; the
interior is broken up. The gelatin is not liquefied. In
gelatin punctures there is no liquefaction observable.
Upon agar-agar the development at the temperature
of the incubator, which is more rapid than that at the
temperature of the room, results in the production of a
The growth upon potato has a brownish color. The